Conventional surface protective layers and interlayer insulating layers for semiconductor devices can include a polyimide resin, which can have excellent heat resistance, electrical characteristics, and mechanical characteristics, among other properties.
Polyimide resins have recently been used in the form of a photosensitive polyimide precursor composition. The polyimide precursor composition can be coated on a semiconductor device, patterned by ultraviolet (UV) rays, developed, and heat imidized to form a polyimide-based resin film, useful as a surface protective layer, an interlayer insulating layer, and the like. Accordingly, it is possible to significantly shorten the process for making a surface protective layer, an interlayer insulating layer, and the like, as compared to processes using conventional non-photosensitive polyimide precursor compositions.
The photosensitive polyimide precursor composition can be applied as a positive type, in which an exposed part is dissolved by development, or as a negative type, in which the exposed part is cured and maintained. Positive type photosensitive compositions can be advantageous because they can be developed by a non-toxic alkali aqueous solution.
A positive photosensitive polyimide precursor composition can include a polyimide precursor of polyamic acid, a photosensitive material of diazonaphthoquinone, and the like. However, the positive photosensitive polyimide precursor composition may not provide a desired pattern because the carbonic acid of the polyamidic acid used can be too highly soluble in an alkali.
In order to solve this problem, Japanese Patent Laid-Open Publication No. H10-30739 is directed to a material including a phenolic hydroxyl acid instead of carbonic acid, which is introduced by esterification of a polyamidic acid with an alcohol compound having at least one hydroxyl group. This material, however, may be insufficiently developed, which can cause problems such as reduced layer thickness or resin delamination from the substrate.
Japanese Patent Laid-open Publication No. S63-96162 is directed to a material prepared by mixing a polybenzoxazole precursor with a diazonaphthoquinone compound. When the polybenzoxazole precursor composition is actually used, however, layer thickness of an unexposed part can be significantly decreased, so that it can be difficult to obtain a desirable pattern after the developing process.
The molecular weight of the polybenzoxazole precursor can be increased to reduce loss of layer thickness of the unexposed part. This can, however, generate development residue (scum), which can deteriorate resolution and lengthen development times of the exposed part.
Japanese Patent Laid-Open Publication No. H9-302221 and Japanese Patent Laid-Open Publication No. 2000-292913 are directed to methods of suppressing loss of layer thickness adding a particular phenol compound to a polybenzoxazole precursor composition. These methods, however, may not sufficiently suppress loss of layer thickness of the unexposed part. Accordingly, there is still a need for a material and method which can prevent or minimize the generation of development residue and also can effectively suppress loss of layer thickness.
Also, phenol used to adjust the solubility can be decomposed or cause a side reaction at a high temperature during thermocuring, or can form micropores in a layer when it is evaporated at a high temperature, which can damage the mechanical properties of a cured film. Therefore, there is also a need for a dissolution controlling agent that can resolve these problems.